1. Field
This disclosure relates to an organic light emitting diode (OLED) display device which can realize an image using an organic emitting material, and a method of fabricating the same.
2. Description of the Related Technology
An OLED display device is a display device emitting light with a specific wavelength using energy generated from excitons generated by recombining electrons and holes, which are injected into an emitting layer from a cathode and an anode.
The OLED display devices are classified into a passive matrix type and an active matrix type. The active matrix OLED display device generally includes two thin film transistors (TFTs) to drive an organic light emitting diode (OLED) including the organic thin film. The two transistors may include a driving transistor applying a driving current to the OLED and a switching transistor transmitting a data signal to the driving transistor, thereby determining on/off of the driving transistor. Thus, compared to the passive matrix OLED display device, it has a relatively more complicated fabricating process.
The passive matrix OLED display device is typically applied in applications such as low-resolution and small-sized display devices. The active matrix OLED display device can generally exhibit stable brightness according to a uniform current provided using the switching and driving transistors disposed in each pixel of a display region, and have low power consumption, so that it can be used in high-resolution and large-sized display devices.
Generally, the thin film transistors, such as the switching or driving transistors include a semiconductor layer, a gate electrode disposed on one side of the semiconductor layer to control current flow by the semiconductor layer, and source and drain electrodes connected to opposite ends of the semiconductor layer, respectively, to transfer a certain amount of current through the semiconductor layer. The semiconductor layer may be formed of polycrystalline silicon (poly-Si) or amorphous silicon (a-Si). Since the poly-Si has a higher electron mobility than the a-Si, the poly-Si is generally more frequently used.
To form a semiconductor layer using the poly-Si, an a-Si layer is typically formed on a substrate and crystallized by one of solid phase crystallization (SPC), rapid thermal annealing (RTA), metal induced crystallization (MIC), metal induced lateral crystallization (MILC), excimer laser annealing (ELA), and sequential lateral solidification (SLS).